US2070473A - Control system - Google Patents

Description

Feb. 9, 1937. I P, RR, R 2,070,473

CONTROL SYSTEM Filed March 28, 1936 RECTIFIER Inventor: Philip I LCurrieT,

b Wan 96.27 L (5 His Attorney.

Patented Feb. 9, 1937 PATENT OFFIE CONTROL SYSTEM Philip M. Currier, Ballston Lake, N. Y., assignor to General Electric Company, a corporation of New York Application March 28, 1936, Serial No. 71,408

2 Claims.

This invention relates to control systems, more particularly to motor control systems, and it has for an object the provision of a simple, reliable and improved system of this character.

More specifically the invention relates to control systems in which a plurality of translating devices, one of which is an electric motor, are arranged to be supplied from a rectifier and a more specific object is the provision of means to provide for the condition of operation of the motor as a generator when an overhauling load is imposed on the motor. The overhauling load condition is frequently encountered in practice, for example, in elevator systems, in which the load on the motor may be either hauling or overhauling depending on the number of passengers in the car. Accordingly, in illustrating this invention in one form thereof, it is shown as embodied in a motor control system in which a plugo rality of motors, such as the driving motors of an elevator system, are arranged to be supplied from a rectifier.

In carrying the invention into effect in one form thereof, a plurality of translating devices, 25 one of which is a direct current motor, are arranged to be supplied from a rectifier and a current consuming device is provided, together with means responsive to overhauling load conditions for connecting the current consuming device in 30 circuit with the motor to provide for generator action.

For a better and more complete understanding of the invention reference should now be had to the following specification and to the accompanying drawing, the single figure of which is a simple, diagrammatical illustration of an embodiment of the invention.

Referring now to the drawing, a plurality of translating devices, such as the direct current electric motors i9 and II, are arranged to be supplied from a rectifier It. The motors l and H are provided with field windings Illa. and Ha, respectively, which are supplied from a suitable source, represented by plus and minus signs. A plurality of line switches it and M are provided for respectively connecting the armatures of motors l9 and ii to the buses 55, which in turn are connected by means of conductors Hi to the output circuit of the rectifier it.

In parallel with the rectifier is a circuit comprising a current consuming device such as the resistance H and an electromagnetically operated contactor l8. In order to provide for operation of the contactor i8 to connect the resistance I! in parallel with the rectifier and therefore in circuit with the armatures of the motors, a plurality of voltage responsive relays l9 and 2t] are connected on the motor side of line switches l3 and [4, so as to be responsive to the terminal voltage of motors l0 and II respectively.

These relays are designed or set to respond to a voltage which exceeds by a predetermined amount the highest voltage that the rectifier can deliver.

The operation of the system is as follows:

The motors l0 and II are connected to the rectifier I2 by closing their respective line switch es I3 and I 4. Either or both of these switches may be closed. If one motor is taking power from the rectifier when the load on the other motor becomes overhauling, the motor which is overhauled can supply power to the first motor. Under these conditions, the voltage of the circuit does not exceed the value at which the voltage relays I9 and 20 are set to respond, and the contactor l8 remains open.

However, if one motor, for example, motor I0 is disconnected and not taking power from the rectifier, and if at the same time the motor H is overhauled by its load, the direction of current through the motor must reverse, and is, therefore, prevented from flowing because current cannot flow backward through the rectifier. As a result of the overhauling load, the terminal voltage of motor I i will rise above the rectifier voltage to the value at which the relay 20 is set to respond. At this voltage, relay 26 will close its contacts to complete an energizing circuit for the operating coil of contactor l8. In responding to energization, this contactor closes its contacts to connect resistance I? in parallel with rectifier l2 and motor I! can now operate as a generator and pump energy into the resistance I! in which it is dissipated in the form of heat. The drop-out voltage of relays l9 and 28 should be adjusted so that they do not drop out when the resistance load is thrown on the regenerating motor.

When line switch Hi is opened and the motor stopped as by a mechanical brake, its voltage decreases below the set value of relay 220, which thereupon opens to deenergize contactor l8 and open the parallel circuit through resistance ll.

Although in accordance with the provisions of the patent statutes, this invention is described as embodied in concrete form, it will be understood that the elements and connections shown are merely illustrative and that the invention is not limited thereto, since alterations and modifications will readily suggest themselves to persons skilled in the art Without departing from the true spirit of the invention or from the scope of the annexed claims.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. A motor control system comprising 2. rectifier, a plurality of direct current motors arranged to be supplied therefrom, a resistance element, a plurality of voltage relays, one for each of said motors and responsive to a rise in the terminal voltage of its associated motor for connecting said resistance in circuit therewith.

PHILIP M. CURRIER.

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